Use Comparator in heap.

src/data-structures/priority-queue/PriorityQueue.js

@@ -1,4 +1,5 @@
 import MinHeap from '../heap/MinHeap';
+import Comparator from '../../utils/comparator/Comparator';
 
 // It is the same as min heap except that when comparing to elements
 // we take into account not element's value but rather its priority.
@@ -6,6 +7,7 @@ export default class PriorityQueue extends MinHeap {
   constructor() {
     super();
     this.priorities = {};
+    this.compare = new Comparator(this.comparePriority.bind(this));
   }
 
   add(item, priority = 0) {
@@ -13,7 +15,7 @@ export default class PriorityQueue extends MinHeap {
     super.add(item);
   }
 
-  compare(a, b) {
+  comparePriority(a, b) {
     if (this.priorities[a] === this.priorities[b]) {
       return 0;
     }